package com.cqnu.util;

import java.util.Random;

public class CharacterUtils {
	public static String getRandomString(int length) {
		//String str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
		String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
		Random random = new Random();
		StringBuffer sb = new StringBuffer();

		for (int i = 0; i < length; ++i) {
			int number = random.nextInt(str.length());// [0,62)
			sb.append(str.charAt(number));
		}
		return sb.toString();
	}

	public static String getRandomString2(int length) {
		Random random = new Random();

		StringBuffer sb = new StringBuffer();

		for (int i = 0; i < length; ++i) {
			int number = random.nextInt(3);
			long result = 0;

			switch (number) {
			case 0:
				result = Math.round(Math.random() * 25 + 65);
				sb.append(String.valueOf((char) result));
				break;
			case 1:
				result = Math.round(Math.random() * 25 + 97);
				sb.append(String.valueOf((char) result));
				break;
			case 2:
				sb.append(String.valueOf(new Random().nextInt(10)));
				break;
			}
		}
		return sb.toString();
	}

	public static void main(String[] args) {
		System.out.println(getRandomString(20));
		System.out.println(getRandomString2(20));
	}
}
